1. Field of the Invention
This invention relates to a process and a control device for a motor output suitable for being controlled through a communication bus and capable of informing a supply side network controller through this bus.
2. Discussion of the Background
The architecture of a low level communication bus (factory bus) usually includes a network controller that is called the "master", and sensors and/or actuators that are called "slaves". This "master" module and these "slave" modules are connected together through a communication support (pair of conducting wires, coaxial cable, optical fiber, carrier current, etc.) which carry information and possibly the power supply for slaves.
The "slave" module may be a motor output, of which there are several types (direct starter, starter with reversed direction of motion, star-delta starter, progressive starter). This type of motor output consists in an electrical switchgear that partially or completely carries out control functions (contactor, static control) and motor protection functions (circuit breaking, magnetic protection, temperature protection, phase unbalance). One or two "on-off" sensors may be connected directly to this motor output if the application needs them. Electronics locally manage all module components and communication on the bus.
The "master" module sends motor output orders (forward motion command, reverse motion command, stop command) through the communication bus. The motor output executes these commands and returns relevant information (moving, stopped, in fault, etc.), together with the state of its remote "on-off" sensors, through this bus. Patent FR 2 732 523 describes a motor output connected to an AS-I (abbreviation for Actuator Sensor Interface) type communication bus.
We will now consider the example of an automation system composed of a conveyer belt, the motor of which is controlled by an actuator connected to the communication bus. In motion, the master is informed through the bus when a part is detected by a remote "on-off" sensor. It must then return a stop order to this actuator in order to stop the belt. The time interval between when the sensor is activated and the time at which the motor output executes the stop order depends on the various points through which the information passes and the master software cycle and processing times. It also, to a lesser degree, depends on the time to distribute the sensor information on the bus and for the master to distribute the stop command. Therefore the system reaction time is highly variable.